Light emitting display and method of manufacturing the same

ABSTRACT

The present invention is to provide an organic light emitting display and a method of manufacturing the same. The light emitting display according to the present invention includes: a first substrate on which a plurality of light emitting devices having first electrodes, organic light emitting layers, and second electrodes are disposed; a second substrate disposed to face the first substrate; a dam member disposed between the first substrate and the second substrate to surround the plurality of light emitting devices; an inorganic sealing material disposed between the first substrate and the second substrate in an outer area of the dam member and attaching the first substrate to the second substrate; and a silicon filling material provided between the first substrate and the second substrate inward of the dam member to be in contact with the second electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/607,864 which is continuation-in-part of U.S. application Ser. No.12/215,610 filed Jun. 27, 2008 which claims the benefit of Korean PatentApplication No. 10-2007-0064293 filed Jun. 28, 2007 in the KoreanIntellectual Property Office, the entire contents of which areincorporated by reference herein. This application also claims thebenefit of Korean Patent Application No. 10-2008-0106222, filed on Oct.29, 2008, in the Korean Intellectual Property Office, the entire contentof which is incorporated herein by reference. In addition, this patentis related to U.S. patent application Ser. No. 12/607,863, filed Oct.28, 2009.

BACKGROUND

1. Field of the Invention

The present invention relates to a light emitting display and a methodof manufacturing the same, and more particularly to a light emittingdisplay having a silicon filling material between a substrate on which alight emitting device is formed and a sealing substrate, and a method ofmanufacturing the same.

2. Discussion of Related Art

Since a light emitting device such as an organic light emitting diode(OLED) includes organic materials vulnerable to moisture and/or oxygen,it is required to protect the OLED against moisture and/or oxygen.

Since a light emitting display using an OLED typically has a wideviewing angle, high contrast and response speed, and low powerconsumption, in spite of its vulnerability to moisture and/or oxygen,light emitting displays are widely used in personal portable equipment,such as MP3 players, mobile telephones, and televisions (TV). Lightemitting displays have been slimmer in accordance with the requests ofusers.

However, when the thickness of a substrate of a light emitting displayis reduced to about 0.3 mm or less in order to reduce the overallthickness of the light emitting display, it is difficult to maintain themechanical integrity of the device under stresses such as falling andtwisting. Loss of mechanical integrity can compromise the sealed stateof the device, thereby reducing the life of the organic light emittingdisplay.

SUMMARY OF THE INVENTION

Accordingly, it is an object to provide a light emitting display capableof securing mechanical reliability and of durability and a method ofmanufacturing the same.

It is another object to provide a light emitting display capable ofsecuring mechanical reliability by using an inorganic sealing materialthat effectively prevents the infiltration of moisture or oxygen and amethod of manufacturing the same.

In order to achieve the foregoing and/or other objects, according to oneaspect of the present invention, there is provided a light emittingdisplay including: a first substrate on which a plurality of lightemitting devices having first electrodes, organic light emitting layers,and second electrodes are disposed; a second substrate disposed to facethe first substrate; a dam member disposed between the first substrateand the second substrate to surround the plurality of light emittingdevices; an inorganic sealing material disposed between the firstsubstrate and the second substrate in an outer area of the dam memberand attaching the first substrate to the second substrate; and a siliconfilling material provided between the first substrate and the secondsubstrate inward of the dam member to be in contact with the secondelectrodes.

In order to achieve the foregoing and/or other objects, according toanother aspect of the present invention, there is provided a method ofmanufacturing a light emitting display including: providing a firstsubstrate on which a plurality of light emitting devices comprisingfirst electrodes, organic light emitting layers, and second electrodesare disposed; providing a second substrate; forming an inorganic sealingmaterial along an outer area in the second substrate; forming a dammember on the second substrate inside the inorganic sealing material andsurrounding the plurality of light emitting devices; dropping aliquid-phase silicon filling material inside the dam member; disposingthe first substrate and the second substrate to face each other so thatthe silicon filling material becomes in contact with the secondelectrodes and fills a space inside the dam member; attaching theinorganic sealing material to the first substrate and the secondsubstrate to seal the plurality of light emitting devices; and hardeningthe silicon filling material.

The present invention as described above seals the light emittingdevices using an inorganic sealing material effectively preventinghydrogen or oxygen from penetrating and fill space between thesubstrates with a silicon filling material to improve pressureresistance. The silicon filling material has a high stability as it doesnot react to the material of the light emitting device. Further, itmaintains pressure resistance between the substrates to allow the sealedstate not to be easily broken by means of impact or the like. Therefore,the mechanical reliability is improved so that the life of the lightemitting display can be increased, and a passivation film for protectinga cathode electrode is omitted so that the manufacturing process can besimplified.

Also, in typical light emitting displays, since the space between thesubstrate and the sealing substrate is empty, the substrate may droop tocause the generation of Newton's ring or the displays may be vulnerableto impact. On the other hand, in the light emitting display according tothe present invention, the space between the substrate and the sealingsubstrate is filled with a filling material having a similarrefractivity to the glass substrate, thereby preventing Newton's ringand having improved visibility.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe preferred embodiments, taken in conjunction with the accompanyingdrawings of which:

FIG. 1 is a perspective view illustrating a light emitting displayaccording to the present invention;

FIG. 2 is a cross-sectional view taken along line I1-I2 of FIG. 1;

FIG. 3 is a cross-sectional view of the light emitting device of FIG. 1;

FIGS. 4A and 4B are plan views illustrating a method of manufacturingthe light emitting display according to the present invention; and

FIGS. 5A to 5F are cross-sectional views illustrating a method ofmanufacturing the light emitting display according to the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description, only certain exemplaryembodiments of the present invention have been shown and described,simply by way of illustration. As those skilled in the art wouldrealize, the described embodiments may be modified in various differentways, all without departing from the spirit or scope of the presentinvention. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. In addition, when anelement is referred to as being “on” another element, it can be directlyon the element or be indirectly on the element with one or moreintervening elements interposed therebetween. Also, when an element isreferred to as being “connected to” another element, it can be directlyconnected to the element or be indirectly connected to the element withone or more intervening elements interposed therebetween. Hereinafter,like reference numerals refer to like elements.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.However, the embodiments set forth herein are provided so that thoseskilled in the art can fully understand the present invention and thus,the present invention can be embodied in different forms and should notbe construed as limited to the embodiments set forth herein.

In order to increase the life of an organic light emitting display, itis effective to use an inorganic sealing material that effectivelyprevents moisture and/or oxygen from penetrating. However, the inorganicsealing material is easily separated by means of impact or warp todeteriorate mechanical reliability.

Therefore, the present invention provides a light emitting display whichis increased in life and improved in mechanical reliability by using aninorganic sealing material that effectively prevents moisture and/oroxygen from penetrating and a method of manufacturing the same.

FIG. 1 is a perspective view illustrating a light emitting displayaccording to the present invention, and FIG. 2 is a cross-sectional viewtaken along line I1-I2 of FIG. 1.

Referring to FIGS. 1 and 2, the light emitting display of the presentinvention includes a substrate 100 on which a plurality of lightemitting devices 130 are formed, a sealing substrate 200 facing thesubstrate 100, a dam member 220 provided between the substrate and thesealing substrate 200 to surround the plurality of light emittingdevices 130, an inorganic sealing material 210 provided outside the dammember 220 between the substrate 100 and the sealing substrate 200 andattaching the substrate 100 to the sealing substrate 200, and a siliconfilling material 300 provided inside the dam member 220 between thesubstrate 100 and the sealing substrate 200.

The substrate 100 is defined as a pixel region 120 and a non-pixelregion 140 around the pixel region 120. The plurality of light emittingdevices 130 are formed in the pixel region 120, and a driving circuit160 for driving the plurality of light emitting devices 130 is formed inthe non-pixel region 140.

Referring to FIG. 3, the light emitting device 130, for example, may beformed of an organic light emitting display that includes an anodeelectrode 131, a cathode electrode 134 and an organic light emittinglayer 133 formed between the anode electrode 131 and the cathodeelectrode 134. The organic light emitting layer 133 is formed in a lightemitting region (a region where the anode electrode 131 is exposed)defined by a pixel definition layer 132 and may include a hole injectionlayer, a hole transport layer, an electron transport layer and anelectron injection layer.

Also, a thin film transistor for controlling the operation and acapacitor for maintaining a signal may be coupled to the light emittingdevice 130. The thin film transistor 110 includes a semiconductor layer112 providing a source and drain region and a channel region, a gateelectrode 114 insulated from the semiconductor layer by a gateinsulating layer 113, and a source and drain electrode 116 coupled tothe semiconductor layer 112 in the source and drain region through acontact hole formed on the insulating layer 115 and the gate insulatinglayer 113. Reference numerals 111 and 117, not explained, are a bufferlayer and a planarization layer, respectively.

The sealing substrate 200 is disposed to overlap with the pixel region120 and a part of the non-pixel region 140. In the case of a frontemission type of display, the sealing substrate 200 can be formed of atransparent material such as glass. In the case of a rear emission type,the sealing substrate can be formed of an opaque material.

The inorganic sealing material 210 includes frit, which is melted by alaser or infrared rays to be attached to the substrate 100 and thesealing substrate 200. The inorganic sealing material 210 is providedbetween the substrate 100 and the sealing substrate 200 to surround thelight emitting device 130 so that moisture or oxygen penetration fromthe outside is prevented.

The dam member 220 prevents the filling material 300 from flowing sothat the shape of the filling material 300 is maintained. The dam member220 is provided to prevent heat from being transmitted to the lightemitting devices 130 when the inorganic sealing material 210 is attachedto the substrate 100 and the sealing substrate 200 and formed of aninorganic material or an organic material.

The inorganic material includes frit. In this case, frit that transmitsor reflects a laser or infrared rays is used or a reflecting layer isformed on the surface of the dam member 220 using metal having a highreflectance in the infrared region, e.g., Au, Ag, Pt, and/or Al, so thata laser or Infrared rays is reflected. In addition, as an organicmaterial, at least one selected from the group consisting of epoxy,epoxy acrylate, and silicones (e.g., bisphenol A type epoxy,cycloaliphatic epoxy resin, phenyl silicone resin or rubber, acrylicepoxy resin, etc. and).

The dam member 220 may be formed to be in contact with the inorganicsealing material 210 or may be parallel separated from the inorganicsealing material 210 by a predetermined distance. For example, the dammember 220 may be formed to be in contact with the inorganic sealingmaterial 210 when including an inorganic material, while it may beseparated from the inorganic sealing material 210 by about 50 μm or morewhen including an organic material. If the dam member 220 of an organicmaterial is in contact with the inorganic sealing material 210, it maybe decomposed by heat when the inorganic sealing material 210 isattached to the substrate 100 and the sealing substrate 200 to generateout gas.

The silicon filling material 300 is provided to fill an inward spacebetween the substrate 100 and the sealing substrate 200 defined by thedam member 220. The silicon filling material 300 is a colorless(transparent) material having a transmittance of not less than 90% in avisible region, such as a glass substrate, so that visibility does notdeteriorate. Also, the silicon filling material 300 has a high stabilityin view of chemistry so that it does not react to a material forming thelight emitting devices 130, in particular, the cathode electrode 134formed of a metal material.

In order to protect the cathode electrode 134 after the light emittingdevice 130 is formed as shown in FIG. 3, an organic or inorganicpassivation film (not shown) should be formed on the cathode electrode134. In this case, an additional process is required and the displayincreases in thickness. However, since the present invention uses thefilling material 300 which does not react to a metal material, it can beimplemented to have a structure where the cathode electrode 134 isexposed, making it possible to simplify the process and structurethereof.

Hereinafter, a method of manufacturing a light emitting displayaccording to the present invention will be described in detail.

FIGS. 4A and 4B are plan views illustrating a method of manufacturingthe light emitting display according to the present invention. FIGS. 5Ato 5F are cross-sectional views illustrating the method of manufacturingthe light emitting display according to the present invention. FIGS. 5Ato 5D are cross-sectional views taken along line I11-I12 of FIG. 4B.

Referring to FIG. 4A, first, the substrate 100 on which the plurality oflight emitting devices 130 are formed is provided. The substrate 100 isdivided into the pixel region 120 and the non-pixel region 140 aroundthe pixel region 120. The plurality of light emitting devices 130 areformed in the pixel region 120 of the substrate, and the driving circuit160 for driving the light emitting devices 130 are formed in thenon-pixel region 140.

Referring to FIG. 3, the light emitting devices 130 include an organiclight emitting device having the anode electrodes 131, the organic lightemitting layers 133, and the cathode electrodes 134. Also, the lightemitting devices 130 may further include thin film transistors (TFT) 110for controlling the operation of the organic light emitting device andcapacitors (not shown) for maintaining signals. A process ofmanufacturing the organic light emitting device is illustrated in theKorean Patent Publications No. 2002-0047889 (published on Jun. 22, 2002)and No. 2003-0092873 (published Dec. 6, 2003).

Referring to FIGS. 4B and 5A, the sealing substrate 200 for sealing thelight emitting devices 130 of the pixel region 120 is provided. Thesealing substrate 200 may overlap with the pixel region 120 and a partof the non-pixel region 140. A transparent substrate such as glasshaving the front emission structure or an opaque substrate having therear emission type can be used as the sealing substrate 200.

An inorganic sealing material 210 is disposed along the edge of thesealing substrate 200. The inorganic sealing material 210 is formed byapplying fit using a dispenser or using a screen printing method. Fritcommonly means a powder-type glass material. However, as used herein,frit refers to paste containing a laser or infrared-ray absorbingmaterial, an organic binder, and a filler to reduce a thermal expansioncoefficient, in a main material such as SiO2. The organic binder andmoisture are removed from the paste fit via a drying or annealingprocess so that the paste frit is hardened. The laser or infrared-rayabsorbing material can include a transition metal compound, for example,a vanadium compound. After the inorganic sealing material 210 isdisposed on the sealing substrate 200, a washing process can befollowed.

Referring to FIGS. 4B, 5B, and 5C, the dam member 220 is formed on thesealing substrate 200 on the inward side of the inorganic sealingmaterial 210 to surround the pixel region 120. The dam member 220 may beformed by applying an inorganic material or an organic material bydispensers or by screen printing. At this time, the amount of theinorganic material or organic material is determined in consideration ofthe distance from the light emitting devices 130 disposed in theoutermost region of the pixel region to the inorganic sealing material210 and the height of the dam member 220. The height of the dam member220 may be determined by the height of the inorganic sealing material210 and is preferably the same or less than the height of the inorganicsealing material 210.

Frit can be used as the inorganic material. In this case, the dam member220 can be formed in a process of forming the inorganic sealing material210. Frit that transmits or reflects a laser or infrared rays is used ora reflecting layer 222 is disposed on the surface of the dam member 220in order to reflect a laser or ultraviolet rays as illustrated in FIG.5B. For example, after applying the paste frit, the paste fit is driedor annealed, and hardened to form the dam member 220. Then, a metal suchas Au, Ag, Pt, or Al having a high reflectance in the ultraviolet-raysregion is applied onto the surface of the dam member 220 to form thereflecting layer 222. In addition, the organic material can be at leastone selected from the group consisting of epoxy, epoxy acrylate, andsilicones (e.g., bisphenol A type epoxy, cycloaliphatic epoxy resin,phenyl silicone resin or rubber, acrylic epoxy resin, etc.).

The dam member 220 may be formed to be in contact with the inorganicsealing material 210, as illustrated in FIG. 5B, or to be separated fromthe inorganic sealing material 210 by a predetermined distance, asillustrated in FIG. 5C. For example, when being formed of an inorganicmaterial, the dam member 220 can be in contact with the inorganicsealing material 210. In this case, the area of the non-pixel region canbe reduced. In addition, when being formed of an organic material, thedam member 220 is preferably separated from the inorganic sealingmaterial 210 by 50 μm or more. Since the organic material typically haslow viscosity to be easily applied, it may be easily collapsed by stresssuch as a pressure difference. Therefore, the dam member 220 is formedand then is pre-hardened to be solid in structure, the dam function canbe reinforced. Therefore, the dam member 220 can be pre-hardened byheat, an electron beam, or ultraviolet rays in accordance with the kindof the organic material so that the dam member 220 is not damaged by thestress in a process of attaching the substrate 100 to the sealingsubstrate 200.

In another embodiment, in a process of forming the inorganic sealingmaterial 210 or the dam member 220, a dummy sealing material (not shown)can be formed of epoxy and frit on the outermost edge of the sealingsubstrate 200. The dummy sealing material is formed on the outside ofthe sealing material 210 to collectively seal up the space between thesubstrate 100 and the sealing substrate 200. In the case of a mothersubstrate, the dummy sealing material is disposed along the outermostedge thereof.

Referring to FIG. 5D, the liquid silicon filling material 300 isprovided on the sealing substrate 200 in the inward region defined bythe dam member 220. The silicon filling material 300 is a colorless(transparent) material having a transmittance of 90% or more in avisible-ray region such as a glass substrate, so that it does notdeteriorate visibility. Also, the silicon filling material 300 has ahigh stability in view of chemistry not to react to a material formingthe light emitting devices 130, in particular, the cathode electrode 134formed of a metal material.

The silicon filling material 300 can be provided by ink-jetting, adispenser, screen printing, one drop filling (ODF), or the like. Forexample, the silicon filling material 300 having a viscosity of 1 to2000 cPs may be stacked on the sealing substrate on the internal side ofthe dam member 220. In this case, the proper amount of the fillingmaterial 300 in proportion to the volume of the internal space can beeasily controlled.

Referring to FIG. 5E, the substrate 100 is disposed to face the sealingsubstrate 200. For example, after the substrate 100 is mounted on anupper chuck of an attaching device and the sealing substrate 200 ismounted on a lower chuck of the attaching device, the substrate 100 andthe sealing substrate 200 are attached to each other. As the substrate100 and the sealing substrate 200 are attached to each other, thesilicon filling material 300 is contacted with the cathode electrode 134to fill a space inside the dam member 220 and is prevented from flowingby the dam member 220 so that the shape is maintained. At this time, thesubstrate 100 and the sealing substrate 200 are attached to each otherunder a pressure lower than atmospheric pressure so that bubbles orvoids are not formed between the substrate 100 and the sealing substrate200. In addition, the substrate 100 and the sealing substrate 200 arepressed together so that the space between the light emitting devices130 and the sealing substrate 200 is completely filled with the fillingmaterial 300.

Referring to FIG. 5F, a laser or infrared rays are irradiated along theinorganic sealing material 210 with the substrate 100 and the sealingsubstrate 200 being attached to each other. As the laser or infraredrays are absorbed to generate heat, the inorganic sealing material 210is attached to the substrate 100 and the sealing substrate 200 bymelting, so that the light emitting devices 130 are sealed. Such asealing process is preferably performed after the dummy sealing materialis hardened so that the space between the substrate 100 and the sealingsubstrate 200 becomes a vacuum.

When a laser or infrared rays are irradiated along the inorganic sealingmaterial 210, a mask or a passivation film (not shown) is used toirradiate a laser or infrared rays to only a desired region. When thedam member 220 includes an inorganic material that transmits or reflectsa laser or infrared rays, or when the reflecting layer 222 is formed onthe surface of the dam member 220, the mask or the passivation film isdisposed only in the pixel region 120 so that a laser or infrared raysare not irradiated. When the dam member 220 includes an organicmaterial, the mask or the passivation film is disposed in the pixelregion 120 and the non-pixel region 140 where the dam member 220 isformed so that a laser or infrared rays do not irradiate.

Assuming that a dam member 220 is not formed, since heat generated inirradiating a laser or infrared rays is easily transmitted to thesilicon filling material 300, the temperature can suddenly rise to causedamage to the light emitting devices 130. However, in the presentinvention, the transmission of heat is effectively reduced or preventedby the dam member 220, thereby making it possible to maintain the regionfilled with the silicon filling material 300 and the shape thereof asthey are.

Thereafter, the silicon filling material 300 is hardened using heat, anelectron beam or ultraviolet rays. At this time, since an out gas may begenerated from the silicon filling material 300, the proportion of acomposition (vinyl polymer, H-polymer, hardening catalyst,anti-hardening agent or the like) is controlled during the preparingprocess of the silicon filling material 300 not to generate the out gasat the time of hardening.

The above embodiment has been described with the inorganic sealingmaterial 210 sealing only the pixel region 120 but does not limit thepresent invention. In other embodiments, the inorganic sealing material210 can further seal the driving circuit 160. In addition, according tothe above embodiment, the inorganic sealing material 210 and the dammember 220 are formed in a single structure on the sealing substrate200. In other embodiments, the inorganic sealing material and the dammember can be formed in a double or multiple structure on the substrate100. For example, the inorganic sealing material 210 may be formed in adouble or multiple structure in order to improve a sealing effect, orthe dam member 220 may be formed in a double or multiple structure inorder to improve a heat shielding effect.

In addition, according to the above embodiment, the filling material 300is filled, before attaching the substrate 100 and the sealing substrate200 to each other. However, the filling material 300 can be filled afterthe substrate 100 and the sealing substrate 200 are attached to eachother depending on material or characteristics the material. Also, inthe embodiment, the inorganic sealing material 210 is attached to thesubstrate 100 and the sealing substrate 200, and then the siliconfilling material 300 is hardened. However, the silicon filling material300 can be hardened before the inorganic sealing material 210 isattached to the substrate 100 and the sealing substrate 200.

As an experimental example, when the silicon filling material 300 isfilled using the ODF process and thermally hardened at a temperature of100° C. or less, no defects in light emitting are observed even if thesilicon filling material 300 is exposed to a high temperature of 85° C.and a high humidity of 85% for 428 hours.

While the present invention has been described in connection withcertain exemplary embodiment, it is to be understood that the inventionis not limited to the disclosed embodiment, but, on the contrary, isintended to cover various modifications and equivalent arrangementsincluded within the spirit and scope of the appended claims, andequivalents thereof.

What is claimed is:
 1. A method of manufacturing a light emittingdisplay comprising: providing a first substrate on which a plurality oflight emitting devices comprising first electrodes, organic lightemitting layers, and second electrodes are disposed; providing a secondsubstrate; forming an inorganic sealing material along an outer area inthe second substrate; forming a dam member on the second substrateinside the inorganic sealing material and surrounding the plurality oflight emitting devices; dropping a liquid-phase silicon filling materialinside the dam member; disposing the first substrate and the secondsubstrate to face each other so that the silicon filling materialbecomes in contact with the second electrodes and fills a space insidethe dam member; attaching the inorganic sealing material to the firstsubstrate and the second substrate to seal the plurality of lightemitting devices; and hardening the silicon filling material.
 2. Themethod as claimed in claim 1, wherein the forming the inorganic sealingmaterial comprises: applying fit paste; and drying or annealing theapplied frit paste.
 3. The method as claimed in claim 1, wherein theforming the dam member comprises: applying fit paste; and drying orannealing the applied frit paste and hardening the frit paste.
 4. Themethod as claimed in claim 1, wherein the dam member is formed to be incontact with the inorganic sealing material.
 5. The method as claimed inclaim 1, wherein the forming the dam member comprises: applying a liquidorganic material to be spaced away from the inorganic sealing material;and pre-hardening the applied liquid organic material.
 6. The method asclaimed in claim 1, wherein the disposing the first substrate and thesecond substrate to face each other is performed at a pressure lowerthan atmospheric pressure.
 7. The method as claimed in claim 1, furthercomprising compressing the first substrate and the second substrate sothat the silicon filling material fills the space between the firstsubstrate and the second substrate inside the dam member.
 8. The methodas claimed in claim 1, wherein the sealing the light emitting devicesfurther comprises attaching the first substrate to the second substrateby melting the inorganic sealing material.
 9. The method as claimed inclaim 8, wherein the inorganic sealing material is melted by a laser orinfrared rays.
 10. The method as claimed in claim 1, wherein the siliconfilling material is hardened using any one of heat, an electron beam andultraviolet rays.